This is a program/project grant to support basic research in areas of molecular and cellular biology which directly relate to the ways in which viruses change normal cells into cancer cells. Over the next five years, our program envisages the close working together of several major research divisions (1) the tumor virus laboratory, (2) nucleic acid and protein structure analysis, (3) the synthesis of proteins, (4) nucleic acid replication, (5) electron microscopy, (6) molecular genetics, (7) mammalian cell genetics, and (8) core facilities. Funds are also requested for tumor virus workshops and meetings.